Difference for capacity

cap_test.go

package captest

import "testing"

func WithCap() {
	sl := make([]int, 500, 1000)
	for i := 0; i < 1000; i++ {
		if i < 500 {
			sl[i] = i
		} else {
			sl = append(sl, i)
		}
	}
}

func WithoutCap() {
	sl := make([]int, 500)
	for i := 0; i < 1000; i++ {
		if i < 500 {
			sl[i] = i
		} else {
			sl = append(sl, i)
		}
	}
}


func BenchmarkWithCap(b *testing.B) {
        // run the Fib function b.N times
        for n := 0; n < b.N; n++ {
                WithCap()
        }
}


func BenchmarkWithoutCap(b *testing.B) {
        // run the Fib function b.N times
        for n := 0; n < b.N; n++ {
                WithoutCap()
        }
}

run with go test -bench=.